Journal of Scientific Research and Reports

Microwave pre-milling treatment may be an alternative to conventional hydrothermal treatment for enhancing rice milling recovery while reducing processing time and water consumption. This study investigated the effects of conditioning moisture content (CMC), microwave power level (MPL), and treatment time (TT) on milling and quality attributes of Punjab Basmati 7 (PB7) rice. Response surface methodology (RSM) was used to develop second-order polynomial models for the process. A three-level central composite design was used to conduct the experiments comprising 17 trials, and responses were predicted for brown rice yield, head rice yield, broken rice percentage, grain surface temperature, grain colour change, milled grain colour change, hardness, and cooking coefficient. The models for brown rice yield, head rice yield, broken rice percentage, grain colour change, milled grain colour change, and hardness were significant (p < 0.05), while the models for grain surface temperature and cooking coefficient were non-significant. Treatment time (TT) was found to be the most significant variable in all significant models. Numerical optimisation was performed, and the optimum conditions were identified to be 12% (w.b.) CMC, 60% MPL, and 120 s TT with an overall desirability of 63.80%. The predicted responses were 78.33% brown rice yield, 59.58% head rice yield, 13.75% broken rice, 1.69 ΔE grain colour change, 1.36 (ΔE) milled grain colour change, and 13.52 N hardness. Experimental results under the optimised conditions were 77.45%, 58.86%, 13.90%, 1.72 ΔE, 1.40 (ΔE), and 13.60 N, respectively, for these responses. The deviations ranged from 0.59-2.94% across the responses. The RSM model was considered adequate for the optimisation of microwave pre-milling treatment of PB7 rice.